The proposed studies seek to evaluate social communication in one species of fish. Interactions between male/male and male/female pairs will be assessed, along with physiological correlates of the agonistic and reproductive behaviors observed. The current approach is an attempt to integrate information concerning animal communication, ethology, and physiological psychology, in the context of a games-theory analysis of territorial behavior. A general goal of the proposed research is to demonstrate the utility and preferability of a games-theory approach in an area long dominated by operant analyses.